The investigators are testing the hypothesis that two ounces of whole-shelled walnuts/day added to the diet of men seeking care for infertility will beneficially affect sperm parameters and fertility. The investigators will compare the walnut intervention to the commonly suggested recommendation of adding an OTC multivitamin supplement to the diet.

Purpose: The investigators are testing the hypothesis that two ounces of whole-shelled walnuts/day added to the diet of men with oligo- astheno- or teratospermia will beneficially affect sperm parameters. The investigators found in a previous study (Robbins et al. 2012, Biology of Reproduction 87(4):101, 1-8.) that walnuts added to a Western diet improved sperm parameters in healthy, young men of unknown fertility and the most improvement occurred in participants with poor sperm parameters at baseline. The investigators now test the walnut dietary intervention in a fertility clinic population known to have poor sperm parameters. The investigators will compare the walnut intervention to the usual care suggestion of adding an OTC multivitamin supplement to the diet. Neither walnuts nor the OTC multivitamin have been tested for efficacy in this fertility clinic population previously.

Methods: A randomized, parallel two-group, dietary intervention trial with single-blind masking of outcome assessors will be conducted with up to 140 men who present for fertility work-up with semen parameters below the 25th centile for count, and 10th centile for motility and/or morphology according to the WHO 5th Edition, Laboratory Manual for the Processing and Examining of Human Semen, 2010. Repeated measures at baseline and 12 weeks include: semen analyses (primary outcome), blood fatty acid/ nutrient profiles (secondary outcomes); IPAQ physical activity questionnaire and IIEF index of erectile function (potential modifiers or confounders). Dietary intake will be assessed throughout using 24-hour ASA dietary recall x 5 and fertility assessed by questionnaire at one year post enrollment.

Inclusion Criteria:

• Age 21 years or older
• Sperm concentration < or = to 41 million per ml
• Sperm motility < or = to 40%
• Normal sperm morphology forms < or = to 5.5%
• Patients of Howard H. Kim, MD seen at the Male Reproductive Medicine and Microsurgery Clinic, Cedars-Sinai Medical Center, Los Angeles, California
• Have eaten walnuts throughout life without adverse reaction

Exclusion Criteria:

• Allergy to walnuts or tree nuts
• Food allergy
• Known genetic cause of infertility
• Known anatomical cause of infertility
• History of seizure disorder